Question

B=2^20-(2^19+2^18+2^17+....+2^1+2^0)

 

Answer 1

B = 2^20 - ( 2^19 + 2^18 + 2^17 + ... + 2^1 + 2^0)

Đặt A = 2^19 + 2^18 + 2^17 + ... + 2^1 + 2^0

A = 2^0 + 2^1 + ... + 2^17 + 2^18 + 2^19

2A = 2^1 + 2^2 + ... + 2^18 + 2^19 + 2^20

2A - A = (2^1 + 2^2 + ... + 2^18 + 2^19 + 2^20) - (2^0 + 2^1 + ... + 2^17 + 2^18 + 2^19)

A = 2^20 - 2^0

A = 2^20 - 1

B = 2^20 - (2^20 - 1)

B = 2^20 - 2^20 + 1

B = 1

               

Answer 2

Đặt A=2^19+2^18+2^17+...+2^1+2^0

    2A=2^20+2^19+2^18+...+2^2+2^1

 2A-A=2^20-2^0

      A=2^20-1

=>B=2^20-A

      =2^20-2^20-1

      =1

Đơn giản như đang giỡn fải ko? k nha!

Answer 3

B = 2^20 - ( 2^19 + 2^18 + 2^17 + ... + 2^1 + 2^0)

Đặt A = 2^19 + 2^18 + 2^17 + ... + 2^1 + 2^0

A = 2^0 + 2^1 + ... + 2^17 + 2^18 + 2^19

2A = 2^1 + 2^2 + ... + 2^18 + 2^19 + 2^20

2A - A = (2^1 + 2^2 + ... + 2^18 + 2^19 + 2^20) - (2^0 + 2^1 + ... + 2^17 + 2^18 + 2^19)

A = 2^20 - 2^0

A = 2^20 - 1

B = 2^20 - (2^20 - 1)

B = 2^20 - 2^20 + 1

B = 1